44 



CLASS MOLLUSCA. 



The Dusty Nkritina, {Seriti/ia pidb'gera.) 



This shell is found in the rivers of India, and is about 

 an inch and a quarter in length. All the species of this 

 .^enus are supposed to inhabit fresh water only. There 

 is a curious fact attached to the history of the Neritina, 

 and of a neighbouring- genus, Nerita, — namely, that 

 when found in a fossil state, th.eir colours are always in 

 good preservation. The species, which are tolerably 

 numerous, are in general natives of hot climates. 



The Viviparous Paludina, (Paludina vivipara.) 



The animal of the genus Paludina is an inhabitant of 

 fresh waters : it takes its specific name from the fact of 

 the young being liatched within the parent shell, and 



PJanorlis corneas. Paludina riripava. Liinwcra stagnaUg. 



deposited in the waters perfectly formed. In nearly the 

 whole of this class the eggs are laid either in water or 

 in the earth, and afterwards hatched after a longer or 

 shorter period. 



